feat(i18n): tools + landing page + doorstop generator in English

Phase 1 of full English translation:
- generate_doorstop_items.py: all 55 items (SG/SYS/SWE/SA/SWA) rewritten in English
- generate_landing_page.py: full UI labels, KPI cards, section headings in English
- traceability.py: docstring, error messages, HTML headers in English
- generate_test_report.py: report content + table headers in English
- All 55 markdown items in safety/sg/, reqs/, arch/ regenerated in English

Still to come:
- demo-epb filled Word docs (PID, plans, safety, manuals, audit artefacts)
- Code comments + test names + CI workflow step names
- README + dev-process repo templates

reqs/sys/SYS-005.md

@@ -1,7 +1,7 @@
 ---
 active: true
 derived: false
-header: 'Hill-Hold am Berg'
+header: 'Hill-hold on an incline'
 level: 1.5
 normative: true
 reviewed: null
@@ -11,6 +11,6 @@ links:
 asil: D
 ---
 
-# SYS-005: Hill-Hold am Berg
+# SYS-005: Hill-hold on an incline
 
-Bei aktivem Hill-Hold (Fahrzeug steht am Hang mit Neigung > 5%, Fahrer betaetigt Bremspedal) uebernimmt das EPB-System die Bremskraft beim Loesen des Bremspedals und haelt diese, bis die Anfahrt erkannt wird. Sicherheitsziel: SG-01.
+When hill-hold is active (vehicle on a slope with grade > 5%, driver pressing the brake pedal), the EPB system shall take over the brake force when the brake pedal is released and shall maintain it until drive-away is detected. Safety goal: SG-002.